Polyphase arc stripper

ABSTRACT

An improved arc stripper for stripping insulation from an electrical wire is provided with three electrodes that are positioned symetrically about a point where the wire is to be stripped. The three electrodes are excited from a three phase power supply and produce an arc that is readily maintained in a position to strip insulation from the wire.

United States Patent [191 Desautels et al.

[ 1 POLYPHASE ARC STRIPPER [75] Inventors: Paul M. Desautels,Poughkeepsie;

Lawrence P. Remsen, Stanfordville,

both of NY.

[73] Assignee: IBM Corporation, Armonk, NY.

[22] Filed: Oct. 17, 1973 [21] Appl. No.: 407,007

[52] U.S. Cl. 219/68; 219/122; 219/383 [51] Int. Cl 823p 1/02 [58] Fieldof Search 219/68, 85, 122, 123, 243,

[56] References Cited UNITED STATES PATENTS 11/1966 De Bolt 219/123 X[451 May 27, 1915 3,505,916 4/1970 Brandt 219/68 X 3,646,307 2/1972Hazel 219/85 X Primary Examiner.l. V. Truhe Assistant ExaminerN. D.Herkamp Attorney, Agent, or FirmW. S. Robertson [57] ABSTRACT Animproved arc stripper for stripping insulation from an electrical wireis provided with three electrodes that are positioned symetrically abouta point where the wire is to be stripped. The three electrodes areexcited from a three phase power supply and produce an are that isreadily maintained in a position to strip insulation from the wire.

7 Claims, 7 Drawing Figures Pmmwwm ms 3.886343 SHEET 2 FIG.3

POLYPHASE ARC STRIPPER RELATED APPLICATIONS US. Pat. No. 3,646,307issued to H. Kenneth Hazel supplements the description in thisspecification by showing an arc stripper and an apparatus for bonding awire from which insulation has been stripped.

INTRODUCTION Stripping insulation from an electrical wire is a familiaroperation in manufacturing electrical apparatus. Commonly, the insulatedwire is gripped by hand or by a mechanical tool and the insulation iscut away from the wire at the point where the wire is to make electricalcontact. There are limitations to these methods when stripping verysmall wires that are used for making connections between integratedcircuit components. It has also been proposed to strip wires by strikingan electric arc in the region of the wire to remove the insulation bymeans of the arc. The cited patent shows one are stripper, and generallysimilar arc strippers have been described in the IBM TechnicalDisclosure Bulletin: Wire Stripper by L. M. Lancaster, Vol. 10,No. 4,September 1967; Electric Arc Stripper by E. H. Empson, Vol. 12, No. 8,Jan. I970; and High- Energy Arc Wire Insulation Removal Tool by P. M.Desautels and H. C. Schick, Vol. 13, No. 12, May 1971.

As these designs for are strippers show, there has been substantialinterest in developing an arc stripper, but shortcomings have been foundin these designs and none of these developments have proceeded beyondlaboratory experiments.

In an arc stripper, a high voltage between a pair of electrodesestablishes a conductive path through the normally non-conducting air inthe neighborhood of the wire that is to be stripped. Positive ions andfree electrons in the air provide the charge carriers. The hightemperature of the arc maintains these charge carriers and the are thustends to avoid a path containing a cooling element such as the walls ofthe supporting structure or the wire that is to be stripped.Accordingly, it has been difficult in known are strippers to maintainthe arc in a position to strip the insulation; an object of thisinvention is to provide a new and improved arc stripper that overcomesthis problem.

SUMMARY OF THE INVENTION In the specific embodiment of the inventionthat will be described later, three electrodes are located symetricallyabout the position where an insulated wire is to be stripped, and theelectrodes are energized from a three phase power supply. An arc isproduced between pairs of electrodes in a three phase sequence. The archas been observed to occur substantially equally along each of the threepaths in close contact with the insulation and thereby to suitably stripthe insulation.

From a more general standpoint, a plurality of electrodes are positionedabout a point where a wire is to be located and periodic voltages areapplied between pairs of electrodes that establish a well defined arcpath over a surface of the wire insulation (rather than through the wireitself or along alternative paths on either side of the wire andinsulation). This are stripper establishes arc paths over a shortcircumference of the wire and thus does not permit alternate paths oneither side of the wire, and it energizes the electrodes periodically tofurther assure that the arc forms along each of these paths.

The following description of the preferred embodiment of the inventionwill suggest to those skilled in the art various other features andadvantages of this invention.

THE DRAWING FIG. I is a simplified isometric view of the preferred arestripper.

FIG. 2 shows a wire from which a region of insulation has been stripped.

FIG. 3 is a side view partially in section of the preferred arcstripper.

FIG. 4 is an enlarged view of a section of FIG. 3 showing the electrodestructure.

FIGS. 5, 6, and 7 are simplified views similar to FIG. 4 showing asequence of steps in a stripping operation.

THE PREFERRED EMBODIMENT OF THE INVENTION Introduction The generalfeatures of the preferred are stripper can be understood from thesimplified isometric drawing of FIG. I. A housing 12 is made ofasuitable arc resistant material such as any suitable ceramic. At itsforward end, the housing has a slot 14 that receives a wire 15 fromwhich the insulation I6 is to be stripped. As the drawing illustrates,the wire is advanced from the stripper with a previously strippedportion in a position for a subsequent operation such as bonding. Thecited patent to H. Kenneth Hazel illustrates the combination of a wirebonder and an arc stripper and will suggest applications of this arestripper to various analogous operations. As FIG. 2 shows, the arcstripper strips the wire 15 clear along a selected length and bevels theinsulation on either side of the stripped portion. With beveledinsulation at the point of stripping, the wire can be more easilypositioned at a point where the bonding operation is to take place.Stripping operations of only a few mills have been made. Longer lengthscan be stripped by increasing the time that the arc is on, by increasingthe voltage, and by repetitive stripping operations.

The rear position of housing 12 has a flange l8 and three electricalconnectors 19, 20 (and 21 not shown) and associated bushings (22 notshown), 23 and 24. As will be explained later, the connectors areattached to conductors that lead to the arc forming components in theregion of the forward end of slot 14. In a typical arc stripper thehousing 12 is about an inch in length, counting flange 18 but notcounting the bushings. The bushings and connectors plug into anelectrical receptacle that provides mechanical support as well aselectrical contact.

The arc stripper is energized from a three phase power supply that hasmeans for independently adjusting the voltage of each phase and hasmeans for timing the duration of an are. A suitable maximum voltage isabout 7,500 volts. A typical operating voltage is about I,SO0 volts, anadvantageously low value. These components are commercially availableand are represented schematically in FIG. 1 by a block 25 and electricallines 26, 27 and 28. The connections to the arc stripper are of coursesuitably insulated and personnel operating or maintaining the arcstripper are suitably protected.

The Arc Forming Components FlGS. 3, 4 and 5 The general features thathave been described so far will be readily apparent in the sectionalside view of HQ. 2 which additionally shows a conductor 30 associatedwith bushing 23 and connector in MG. 1. Conductor and two similarconductors 31, 32 are shown in FIG. 4. Conductors 30, 31, 32 arearranged substantially symetrically about a point 35 in slot 14 where awire that is to be stripped is to be located. In the preferredembodiment of the invention, the wires 30, 31, and 32 are given a squarecut end as shown in H6. 3 to have a sharp edge for better initiating anarc. The conductors are made of a suitable arc withstanding ma-- terialsuch as molybdenum. and housing 12 is formed with holes for receivingthe conductors.

Small holes 37, 38. 39 provide an arc path between the electrodes and anare receiving space formed by slot 14. We have found that the diameterof these holes should be about twice the diameter of the wire that is tobe stripped. Thus, a wire of 1 mil diameter with a l mil radius ofinsulation has a 3 mil diameter, and holes 37, 38, 39 are preferably 6mils in diameter. As HGS. 2 and 3 show, the arc holes and holes for theconduc tors and electrodes are preferably formed from one outer surfaceof housing 12 to another and are closed at one end by plugs 41. -12.

Thus, in the region of holes 37, 38 and 39, conductors 3U, 31 and 32form electrodes and elsewhere they form means to carry current to theelectrodes. (An alternate embodiment of the invention. that will be described later has distinct electrodes and current carrying conductors.)

Operation FIGS. 5. 6 and 7) FIGS. 5, 6, and 7 are each a simplified viewof FIG. 3 showing the electrodes and the arc in relation to an insulatedwire l5, 16 that is to be stripped. As these fig ures represent, an arenormally forms only between two electrodes. The polyphasc excitation ofthe electrodes causes the arc to move around the wire in a way that isanalogous to the rotating motion of a magnetic field in a polyphasemotor. In the sequence of FIGS. 5, 6 and 7, the arc rotates clockwise.Notice that each arc path is to one side of the wire, Thus, the arc isreadily main tained in a position to strip the insulation 16 from wire15.

OTHER EMBODIMENTS OF THE INVENTION The operating principles of thepreferred embodiment of the invention can be achieved in variousstructures. For example, the slot 14 is preferred for most wirestripping and subsequent operations, but alternatively a hole can beprovided in housing l2 and the insulated wire can he threaded throughthe hole. The structure shown in the sectional view of PK] 4 can beformed by two ceramic plates, one of which is flat and one oi which hasgrooves that establish the holes for the electrodes and holes 37, 38. 39for the are when the two plates are lit togetherv In this embodiment,the electrodes are preferably formed of flat. pointed, conductors thatare connected to electrical wires that sup ply electrical power.

The arts of manufacturing arc producing structures are well developedand those skilled in the art will recognize many variations in thedisclosed embodiments of the invention within the spirit. of theinvention and the scope of the claims.

What is claimed is:

1. Apparatus for stripping insulation from a wire comprising,

at least three electrodes,

insulating means of supporting said electrodes about a point midwaybetween said electrodes and rneans for locating a wire to be stripped atsaid point,

a polyphase power supply connected to said electrodes to produce arcsbetween pairs of electrodes in a rotating sequence for strippinginsulation from a wire.

2. The apparatus of Claim 1 wherein said insulating means has a slot forreceiving a wire at said point and the walls ol said slot are shaped tolocate the wire at said point 3. The apparatus of claim 2 wherein saidelectrodes are positioned about said point in a plane that is substantially orthogonal to the path ol a wire to be stripped and arespaced apart by about 4. Apparatus for stripping insulation from a wirecomprising.

at least three electrodes,

electrode supporting means having a wire receiving space, means forsupporting said electrodes about a point in said space midway betweensaid electrodes, means for locating a wire at said point, and having arctransmitting holes between said electrodes and the wire receiving space,

a polyphase power supply connected to said electrodes to produce arcsbetween pairs of electrodes in a rotating sequence for strippinginsulation from a wire at said point,

5. The apparatus of claim 4 wherein the diameter of said aretransmitting holes is substantially twice the diameter of the wire thatis to be stripped.

6. The apparatus of claim 4 wherein said apparatus has three electrodesand said power supply has three phases.

7. The apparatus of claim 6 wherein said power supply is adjustable involtage for each phase and includes means for timing an are that isapplied to strip a wire.

1. Apparatus for stripping insulation from a wire comprising, at leastthree electrodes, insulating means of supporting said electrodes about apoint midway between said electrodes and means for locating a wire to bestripped at said point, a polyphase power supply connected to saidelectrodes to produce arcs between pairs of electrodes in a rotatingsequence for stripping insulation from a wire.
 2. The apparatus of claim1 wherein said insulating means has a slot for receiving a wire at saidpoint and the walls of said slot are shaped to locate the wire at saidpoint.
 3. The apparatus of claim 2 wherein said electrodes arepositioned about said point in a plane that is substantially orthogonalto the path of a wire to be stripped and are spaced apart by about 120*.4. Apparatus for stripping insulation from a wire comprising, at leastthree electrodes, electrode supporting means having a wire receivingspace, means for supporting said electrodes about a point in said spacemidway between said electrodes, means for locating a wire at said point,and having arc transmitting holes between said electrodes and the wirereceiving space, a polyphase power supply connected to said electroDesto produce arcs between pairs of electrodes in a rotating sequence forstripping insulation from a wire at said point.
 5. The apparatus ofclaim 4 wherein the diameter of said arc transmitting holes issubstantially twice the diameter of the wire that is to be stripped. 6.The apparatus of claim 4 wherein said apparatus has three electrodes andsaid power supply has three phases.
 7. The apparatus of claim 6 whereinsaid power supply is adjustable in voltage for each phase and includesmeans for timing an arc that is applied to strip a wire.